I just got a 1.2 farad cap for my audio system. I am pulling about 600rms of class A/B (therefore, inefficient power) off my alternator which is 85 amp. The lights and voltage were both going just slightly more out of control than I wanted. Instead of investing 200-300 dollars in something that will allow me to spend more money (which I can't afford) I got a $40 cap from Circuit City where I work just to SEE what it would do since I can return it no problem. The lights still dim just a little which I don't mind, but overall I think the subs are much quicker hitting and the lights don't dim as much and the voltage stays pretty steady. I am pleased so far. Not recommending it to everyone, just thought I would say you might want to try one unless its obvious you are killing your alternator.
bottom line is caps are for minor electrical problems. I still won't recommend caps for 90% of peoples problems who are pushing a Kicker 2500.1 off of a stock 100 amp alt.
capacitors have a purpose, hence the reason they were designed for use in car audio!
the problem is 99% of the people that buy caps buy them for the wrong reason... Chris - that amp is drawing a decent amount of current, but you're probably OK... the caps not really helping you, if anything it's putting more of a strain on your electrical system.
the lights dimming is not the only symptom of a strain though; it's just the most apparent. The cap is helping in that category b/c it's filling in the quick current demands of the amp (like in a bass kick) that the alt can respond to quickly enough. but then remember the cap is going to recharge itself (putting more strain)... it's more of a bandaid I guess... Getting the HO alt would allow your voltage to stay higher and more constant (keeping your lights bright all the time). I have a HO alt and my lights still dim slightly, a cap would probably help me (for the right reasons). Alternators/batteries cannot react quickly enough (capacitors are designed to release all of their stored energy over a very short amount of time).